The present technology generally relates to flexibly damped mounting assemblies for planetary gear boxes in geared aircraft engine architectures.
Rotating equipment such as aircraft engines are subjected to rotating loads due to rotor imbalance. These vibrations generated by the rotating assembly produce dynamic bearing loads that are transmitted to the engine frame. In efforts to isolate the engine structure from rotating forces, main shaft bearings have historically been “soft-mounted” on flexible supports in combination with squeeze film dampers (SFDs). This type of bearing support reduces vibration transmissibility to the engine structure and also reduces overall dynamic bearing loads. For aircraft engine main shaft bearings, the SFD is a full circular damper which operates on the principle of energy dissipation in the squeeze film land, and may incorporate end seals. These dampers, used since the 1970's, are in virtually every aircraft engine.
Future aircraft engine architectures are leveraging the use of a planetary gearbox between the fan and low pressure turbine (LPT) in efforts to operate the LPT at higher speeds while operating the fan at lower speeds. This configuration enables higher bypass ratios which then leads to lowered specific fuel consumption. However, with the addition of a planetary gear box additional rotating imbalance loads and dynamic gear loads will be generated.